The present invention relates in general to an apparatus for performing tests and measurements on various samples such as sera, and in particular, it relates to a novel motor control means for accurately controlling a reversible electric motor in an apparatus for performing such tests and in other, more general applications. In the related application, an apparatus is disclosed for performing tests and measurements on various liquid samples, in particular sera. The apparatus employs three identical juxtaposed trays each of which are provided with a plurality of receptacles. The first tray includes storage vessels for samples to be tested. The second and third trays serve as processing vessels. Situated above the trays are three independently movable pipettes. Each of the pipettes is situated on carriages which are translatable in a horizontal plane above the trays to position the pipettes over particular receptacles. The pipettes are also translatable in the vertical direction for adding or discharging sera sample, reagents, etc. into particular receptacles. Movement of each of the pipettes in the horizontal and vertical directions is accomplished by means of small electric motors.
It is extremely important that the electric motors utilized for translation of the pipettes be able to operate at high speed and with extreme accuracy. Moreover, it is essential that such electric motors be extremely compact.
It is an object of the present invention to provide a motor control means for accurately controlling a reversible electric motor in the aforementioned and other apparatus which is capable of high speed operation and yet which is extremely accurate.
It is another object to provide such a motor control means which is very compact.
It is another object of this invention to provide means for continuously and unambiguously tracing the position of a motor, and thus the location of the element being driven thereby, as the motor is driven in either a forward or reverse direction.
It is another object of this invention to provide a drive control for a motor, whereby the motor is normally driven at a maximum speed toward its destination and is controlled to decelerate only when it is within a predetermined range from the destination.
It is another object of this invention to provide a digital motor control adaptable to drive a motor through any desired range of steps, or increments, and to control change of motor speed within a range of increments which can be selected as a design parameter.